HTML tag is visible in permission page

Small patch attached to implement the "inline_template" type.

Updated the issue summary to match template, added screenshot, confirmed issue.

Tested Patch in #4 via simplytest.me

Tested:
Go to /admin/people/permissions
Scroll down the page

Confirmed > no more raw HTML tags visible
(Issue Review and test part of #Drupal8nz)

I am not sure if this needs further review before it can go RTBC so I leave it as needs review :). Ta!

And screenshot after patch was applied

+++ b/core/modules/user/src/Form/UserPermissionsForm.php
@@ -140,18 +140,16 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         $form['permissions'][$perm]['description'] = array(
-          '#wrapper_attributes' => array(
-            'class' => array('permission'),
...
+          '#template' => '<div class="permission"><span class="title">{{ title }}</span><div class="description">{% if item_warning %}<em class="permission-warning"> {{ item_warning }}</em> {% endif %}{{ user_permission_description }}</div></div>',

It is much better to have an explicit div than a wrapper_attribute thing.

Can we have a screenshot in non compact mode - ie have the descriptions on the permissions page.

+++ b/core/modules/user/src/Form/UserPermissionsForm.php
@@ -140,18 +140,16 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         if (!$hide_descriptions) {
           $user_permission_description = $perm_item['description'];
-          // Append warning message.
-          if (!empty($perm_item['warning'])) {
-            $user_permission_description .= ' <em class="permission-warning">' . $perm_item['warning'] . '</em>';
-          }
...
+            'user_permission_description' => $user_permission_description,
+            'item_warning' => $perm_item['warning'],

This looks dangerous code and the logic has changed the warning will be displayed regardless of whether the descriptions are hidden. Perhaps we could just swap the order of everything around. For example:

        $form['permissions'][$perm]['description'] = array(
          '#type' => 'inline_template',
          '#template' => '<div class="permission"><span class="title">{{ title }}</span>{% if description or warning %}<div class="description">{% if warning %}<em class="permission-warning"> {{ warning }}</em> {% endif %}{{ description }}</div>{% endif %}</div>',
          '#context' => array(
            'title' => $perm_item['title'],
          ),
        );
        // Show the permission description.
        if (!$hide_descriptions) {
          $form['permissions'][$perm]['description']['#context']['description'] = $perm_item['description'];
          $form['permissions'][$perm]['description']['#context']['warning'] = $perm_item['warning'];
        }

You were right, thanks alexpott.
Changed the logic of the patch as mentionned.

Screenshot with hidden description :

@Haza nice work! How about a screenshot with descriptions?

Whoops, forgot that :)
Here it is :

Looks good!

Committed 9ff1ef3 and pushed to 8.0.x. Thanks!